Matrix display device with multiple line addressing

ABSTRACT

Matrix display device ( 1 ) wherein multiple line addressing is performed by a unit (LD). As a consequence of the multiple line addressing, there is a difference between the luminance values actually displayed (C) and the original luminance values (D). The visible effects of said difference or error (E) are minimized by subtracting said difference or part thereof from the original luminance values, either from neighbouring pixels to be displayed and/or from the same pixels of the subsequent frame. Said neighbouring pixels are preferably the pixels directly below or to the right of the ones considered. The latter is obtained by applying a sample delay to the error (E).

FIELD OF THE INVENTION

[0001] The invention relates to a matrix display device for displayingluminance values, wherein a common value is determined for a group oflines and addressed simultaneously to said group of lines. This isperformed, for example, when said luminance values are coded insubfields and some of the least significant subfields are replaced by acommon value.

[0002] The invention also relates to a method of determining newluminance values based on original luminance values to be displayed on amatrix display device.

[0003] The invention is applicable in, for example, to plasma displaypanels (PDPs), plasma-addressed liquid crystal panels (PALCs), liquidcrystal displays (LCDs), Polymer LEDs (PLEDs), Electroluminescent (EL),Digital Micromirror Devices (DMDs), used for personal computers,television sets and so forth.

BACKGROUND OF THE INVENTION

[0004] A matrix display device comprises a first set of data lines(rows) r₁ . . . r_(M) extending in a first direction, usually called therow direction, and a second set of data lines (columns) c₁ . . . c_(N)extending in a second direction, usually called the column direction,intersecting the first set of data lines, each intersection defining apixel (dot).

[0005] A matrix display device furthermore comprises means for receivingan information signal comprising information on the luminance values oflines to be displayed and means for addressing the first set of datalines (rows) r₁, . . . r_(N) in dependence on the information signal.Luminance values are hereinafter understood to be the grey level in caseof monochrome displays, and each of the individual levels in colour(e.g. RGB) displays.

[0006] Such a display device may display a frame by addressing the firstset of data lines (rows) line by line, each line (row) successivelyreceiving the appropriate data to be displayed.

[0007] In order to reduce the time necessary for displaying a frame, amultiple line addressing method may be applied. In this method, morethan one, usually two, neighbouring, and preferably adjacent lines ofthe first set of data lines (rows) are simultaneously addressed,receiving the same data.

[0008] This so-called double line addressing method (when two lines aresimultaneously addressed) effectively allows speed-up of the display ofa frame, because each frame requires less data, but this is at theexpense of a loss of the picture quality with respect to the originalsignal, because each pair of lines receives the same data, which inducesa loss of resolution and/or of sharpness due to the duplication of thelines.

[0009] These known methods allow a reduction of the addressing time.However, there may be a difference, and in some instances a largedifference, between the original luminance values to be displayed andthe new luminance values actually displayed. This difference, induced bythe line doubling or grouping, hereifafter called “error”, causes a lossin spatial resolution, and increases visible noise-like artefacts,comparable to quantization.

[0010] For the above-mentioned matrix display panel types, thegeneration of light cannot be modulated in intensity to create differentgrey scale levels, as it is the case for CRT displays. On said matrixdisplay panel types, grey levels are created by modulating in time: forhigher intensities, the duration of the light emission period isincreased. The luminance data are coded in a set of subfields, eachhaving an appropriate duration or weight for displaying a range of lightintensities between a zero and a maximum level. The relative iweight ofthe subfields may be binary (i.e. 1, 2, 4, 8, . . . ) or not. Thissubfield decomposition, described here for grey scales, will also applyhereinafter to the individual colours of a colour display. Line doublingor grouping is particularly useful in display panels using subfields, inorder to reduce the addressing time.

[0011] In order to reduce loss of resolution, partial line doubling,i.e. line doubling for only some less significant subfields (hereinafterreferred to as LSB subfields), can be performed. Indeed, the LSBsubfields correspond to a less important amount of light, and partialline doubling will give less visible loss in resolution.

[0012] When more than two lines are addressed simultaneously for someless significant subfields, partial line grouping is performed.Considerations about partial line doubling will hereinafter also apply,mutatis mutandis, to partial line grouping of more than two lines.

[0013] In performing the partial line doubling method, a compromise mustbe sought. Only a few LSB subfields doubled would give a little gain oftime. Too many subfields doubled would give an unacceptable loss ofpicture quality.

[0014] Another aspect that influences the quality is the method ofcalculating the new data of doubled subfields. Different calculationmethods giving different results can be used. The method used shouldgive the best picture quality, as seen by the observer's eyes.

[0015] As the LSBs are doubled in partial line doubling, the value ofthe LSB data for two neighbouring or adjacent lines must be the same.The following methods may be used for the calculation of these data:

[0016] 1. The LSB data of odd lines is used on the adjacent even lines(simple copy of bits).

[0017] 2. The LSB data of even lines is used on the neighbouring oradjacent odd lines (simple copy of bits).

[0018] 3. The average LSB data of each pair of pixels is used for bothnew LSB values.

SUMMARY OF THE INVENTION

[0019] It is an object of the invention to provide a matrix displaydevice with line doubling or grouping, and a method of calculating newdata to be displayed on said matrix display device where loss ofresolution and/or visibility of noise-like artefacts is reduced, andpreferably minimised.

[0020] To this end, a first aspect of the invention provides a matrixdisplay device as defined in claim 1, providing a diffusion of the errorinduced by the line doubling or grouping either to neighbouring pixelsto be displayed in the current frame and/or to neighbouring pixels of asubsequent frame. The visible error induced by line doubling or groupingis thereby reduced. Dependent claims 2 to 4 provide a specific diffusionof the error to the right-hand pair or group of pixels, the pair orgroup of pixels immediately below the one considered, and the same pairor group of pixels in the subsequent frame, respectively. Diffusing theerror to the right-hand pair or group of pixels diffuses the error tothe nearest pixels.

[0021] Simple embodiments, requiring a small number of components whenimplemented in hardware, are the subjects of depenent claims 2 to 4.

[0022] Dependent claim 2 relates to diffusion of the error to one ormore neighbouring pixels on the same line.

[0023] Dependent claim 3 relates to diffusion of the error to one ormore neighbouring pixels in a subsequent pair or subsequent pairs oflines.

[0024] Dependent claim 4 relates to temporal diffusion of the error tothe same or neighbouring pixels.

[0025] Claim 5 relates to the case where luminance values are coded insubfields.

[0026] A second aspect of the invention provides a method as defined inclaim 7. Dependent method claims 8 to 12 correspond to device claims 2to 7, respectively.

[0027] These and other aspects of the invention are apparent from andwill be elucidated with reference to the embodiment(s) describedhereinafter with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In the drawings:

[0029]FIG. 1 schematically shows a matrix display device according tothe invention;

[0030]FIG. 2 is a detailed view of unit (3) of the invention, accordingto a first embodiment of the invention;

[0031]FIG. 3 is a detailed view of unit (3) of the invention, accordingto a second embodiment of the invention;

[0032]FIG. 4 is a detailed view of unit (3) of the invention, combiningfeatures of the first and second embodiment of the invention;

[0033]FIG. 5 is a detailed view of unit (3) of the invention, accordingto a third embodiment of the invention;

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

[0034]FIG. 1 is a schematic diagram of a matrix display device 1comprising a matrix display panel 5, showing a set of display lines(usually directed in the row direction and in this case called rows) r₁,r₂, . . . r_(i),r_(i+1), . . . r_(M). The matrix display panel 5 furthercomprises a set of data lines (columns, not shown) extending in a seconddirection usually being the column direction, intersecting the first setof data lines, each intersection defining a pixel (dot, not shown).

[0035] The matrix display furthermore comprises a circuit 2 forreceiving an information signal D comprising information on theluminance of lines to be displayed and a driver circuit 4 for addressingthe set of data lines (rows r₁, . . . r_(M)) in dependence on theinformation signal D which signal comprises original pixel luminancevalues d₁₁, . . . d_(j) . . . d_(MN).

[0036] The display device 1 in accordance with the invention comprises aunit 3 for determining new pixel luminance values c₁₁, . . . c_(MN) ofpixels, shown as C in FIG. 1, on the basis of original pixel luminancevalues d₁₁, . . . d_(ij) . . . d_(MN) using any line doubling orgrouping method.

[0037] Detailed views of unit 3, shown in FIGS. 2 to 5, show a ‘LD’block, a line grouping circuit performing the line doubling or groupingalgorithm, in accordance with one of different methods, wherein a newcommon value for groups of adjacent or neighbouring lines is determined.In displays where subfields are used, this may be performed for onlysome least significant subfields.

[0038] Unit 3 comprises a subtractor 10 which subtracts a correctionvalue signal E′ supplied by processor unit 11 from the original lineluminance values d₁₁, . . . d_(ij) . . . d_(MN) to supply differencevalues DF (df₁₁, . . . df_(ij) . . . df_(MN)) to the line groupingcircuit LD. The line grouping means may be constituted by or compriseany hardware (such as a circuit shown in FIG. 3 or an arrangement ofcircuits, forming a line-grouping circuit) or software (such as acomputer program or part of a computer program in a microprocessor),which may be specifically incorporated for this function or may be amulti-purpose microprocessor with which more functions are performed,thus forming a piece of software to perform the line doubling function).If a signal E is zero the original line luminance value and thedifference value are of course one and the same. An error-determiningunit 12 determines the error between the difference line luminancevalues DF and the new line luminance value C. This error signal E isconverted into a correction value signal E′ in processor unit 11.

[0039] According to the present invention, the following operations Athru C are performed by unit 3:

[0040] A: The differences e_(ij) and e_(i+lj) between the line-doublingcomputed pixel luminance values c_(ij), c_(i+1j), and the differencepixel luminance values, df_(ij), df_(i+1,j) of pixels ij and i+1,j arecomputed:

e _(ij) =c _(ij) −df _(ij)

e _(i+1,j) =c _(i+1,j) −df _(i+1,j)

[0041] In FIGS. 2 to 5, said method step is depicted by errordetermining unit 12 and the signals going into and out of this unit 12.These differences are a measure of the excess of the luminance C_(ij)effectively shown with respect to the original luminance df_(ij), i.e.of the error introduced by line doubling. The set of differencesconstitutes the error signal E. This error signal is shown as E in FIGS.2 to 5. In formula this can be denoted as E=C−DF

[0042] B: The error E, or part thereof, is diffused, or subtracted fromneighbouring pixels and/or to the same pixels of subsequent frames. Tothis end, the error signal E is converted in processor unit 11 into acorrection value signal E′, which is actually a set of correctionvalues. In formula, E′=conversion of E.

[0043] C: Finally E′ is subtracted in subtractor 10 from D to give DF.In formula, DF=D−E′

[0044] Methods of diffusing the errors are AA thru DD as listed below:

[0045] AA: horizontal feedback (sample delay), as shown in FIG. 2: theerror E, or part thereof, is subtracted from the original luminancevalues d_(i,j+1), d_(i+1,j+1) of the pixels located on the same pair oflines, on the next column j+1, one step further to the right:

df _(i,j+1) :=d _(i,j+1) −F _(h) *e _(i,j)

df _(i+1,j+1) :=d _(i+1,j+1) −F′ _(h) *e _(i+1,j)

[0046] In this example, the correction value signal E′ is constituted bythe set of signals F_(h)*e_(i,j);F′_(h)*e_(i+1,j), etc. to be subtractedfrom d_(i,j+1); d_(i+1,j+1), etc. The coefficients F, F′ determine thetransfer or diffusion of the error to neighbouring pixels.

[0047]FIG. 2 shows a unit 3 for performing horizontal feedback. This isa simple embodiment of the invention, requiring a small number ofcomponents when implemented in hardware. As the error is diffused to thenearest possible pixels, the visual effect of line doubling issignificantly reduced.

[0048] The error is preferably further diffused by subtracting a part ofthe error from the next nearest neighbouring pixel, a smaller part fromthe next nearest neighbouring pixel, etc. i.e.

df _(i,j+1) :=d _(i,j+1) −F _(h) *e _(i,j) −F″ _(h) *e _(i−1,j)

df _(i+1,j+1) :=d _(i+1,j+1) −F′ _(h) *e _(i+1,j−) F′″ _(h) *e _(i,j)

[0049] The coefficients F, F′, F″, F′″ determine the amount of diffusionof the errors over neighbouring and next-neighbouring pixels.

[0050] BB: vertical feedback (2 lines delay), as shown in FIG. 3: theerror, or part thereof, is subtracted from the original pixel luminancevalues d_(i+3j), d_(i+4j of) the pixels located on a pair of lines, twosteps further below, and on the same columns j:

df _(i+2,j) :=d _(i+2,j) −F _(v) *e _(i,j)

df _(i+3,j) :=d _(i+3,j) −F′ _(v) *e _(i+1,j)

[0051]FIG. 3 shows a unit 3 for performing vertical feedback. Thissimple embodiment of the invention also requires a small amount ofhardware. The distance between the pixels where the error is introducedand the pixels where this error is diffused is slightly larger. Theerror is preferably further diffused by subtracting a part of the errorfrom the next-nearest neighbouring pair of lines, a smaller part fromthe next-nearest neighbouring pixel, etc.

df _(i+2,j) :=d _(i+2,j) −F _(v) *e _(i,j) −F″ _(v) *e _(i−2,j)

df _(i+3,j) :=d _(i+3,j) −F′ _(v) *e _(i+1,j) −F′″ _(v) *e _(i−1,j)

[0052] CC: Two-dimensional feedback (1 sample delay and 2 lines delay),as shown in FIG. 4: part of the error is subtracted from the originalpixel luminance values of the pixels located on the same pair of lines,one step further to the right, and part of the error is subtracted fromthe original pixel luminance values of the pixels located on a pair oflines, two steps further below, and on the same columns:

d _(i+2j+1) :=d _(i+2,j+1) −F _(h) *e _(i+2,j) −F _(v) *e _(i,j+1)

d _(i+3,j+1) :=d _(i+3,j+1) −F′ _(h) *e _(i+3,j) −F′ _(v) *e _(i+1,j+1)

[0053]FIG. 4 shows a unit 3 for performing two-dimensional feedback. Bycombining horizontal and vertical feedback, better results can beachieved.

[0054] Again, diffusion of a part of the error may be subtracted fromthe next nearest neighbouring pixel or pair of lines and a smaller partfrom the next-nearest neighbouring pixel or pair of lines.

[0055] DD: Temporal feedback (1 frame delay), as shown in FIG. 5: theerror e_(ij)(t) and e_(i+1,j)(t) for the frame displayed at time t, orpart thereof, is subtracted from the original pixel luminance valuesd_(i,j)(t+1), d_(i,j)(t+1) of the same pixels of the subsequent frame,displayed at time t+1.

[0056]FIG. 5 shows a unit 3 for performing temporal feedback. The bestresults can be obtained by combining horizontal, vertical and temporalfeedback.

[0057] Although the above embodiments relate to line doubling, theapplication to the grouping of three or more lines will bestraightforward to those skilled in the art.

[0058] In the above, the sign := means that the element on the left ofthe sign is replaced by the value on the right. In FIGS. 2 to 5, the “/”and the number 2 near signal lines indicate that these are double lines.

[0059] The parameters F_(h), F_(v), F′_(b), F′_(v) etc, hereinafter alsodenoted as ‘feedback coefficients’ may be given any value foundconvenient by experience. It is advantageous to give these parametersthe value 1 in the case of horizontal and vertical feedback, and valuessuch that F_(h)+F_(v)=1, F′_(h),+F′_(v)=1 i.e. the sum of all feedbackcoefficient F for a particular error value e_(ij) is 1. In the case oftwo-dimensional feedback, this ensures that the total luminance of thepicture is kept constant. By giving these feedback coefficients or thesum of these feedback coefficients values of less than 1, only part ofthe error is diffused.

[0060] The following table depicts schematically exemple values forfeedback coefficients F_(h), F′_(h), . . . and F_(v), F′_(v), . . . indifferent embodiments.

[0061] Simple Horizontal feedback, see FIG. 2 Next-next- Pixel Nearestpixel Next-nearest pixel nearest pixel Same pair of 0 1 0 0 linesNearest pair of 0 0 0 0 lines Next-nearest 0 0 0 0 pair of linesNext-next- 0 0 0 0 nearest pair of lines

[0062] In this example it thus holds

df _(i,j+1) :=d _(i,j+1) −e _(i,j)

df _(i+1,j+1) :=d _(i+1,j+1) −e _(i+1,j)

[0063] This is an example of the subject of dependent claim 2, in itssimplest form, i.e. the embodiment wherein the subtractor (10)subtracts, in operation, said differences e_(ij), . . . e_(i+g−1,j) orpart thereof from the original luminance values d_(ij+1), . . .d_(i+g−1,j+1) of pixels located on the next column j+1 and the samelines i, . . . i+g−1.

[0064] Horizontal feedback over more than one pixel Next-next- PixelNearest pixel Next-nearest pixel nearest pixel Same pair of 0 0.6 0.30.1 lines Nearest pair of 0 0 0 0 lines Next-nearest 0 0 0 0 pair oflines Next-next- 0 0 0 0 nearest pair of lines

[0065] In this example it thus holds

df _(i,j+1) :=d _(i,j+1)−0.6*e _(i,j)−0.3*e _(i−1,j)−0.3*e _(i−2,j)

df _(i+1,j+1) :=d _(i+1,j+1)−0.6*e _(i+1,j−)0.3*e _(i,j)−0.1*e _(i−1,j)

[0066] This is an example of the embodiment as claimed in claim 2 in amore general form, i.e. the subtractor (10) subtracts, in operation,said differences e_(ij), . . . e_(i+g−1,j) or part thereof from theoriginal luminance values d_(i,j+1), . . . d_(i+g−1,j+1) of pixelslocated on the next column j+1 and/or a subsequent column j±2, j+3, (inthis embodiment unit j+3) . . . and the same lines i, . . . i+g−1.

[0067] Instead of the coefficients 06, 0.3, 0.1, in practice, also theset of coefficients {fraction (9/16)}, {fraction (5/16)}, ⅛ appeared toyield good results.

[0068] Vertical feedback over one pair of lines, see FIG. 3 Next-next-Pixel Nearest pixel Next-nearest pixel nearest pixel Same pair of 0 0 00 lines Nearest pair of 1 0 0 0 lines Next-nearest 0 0 0 0 pair of linesNext-next- 0 0 0 0 nearest pair of lines

[0069] In this example it thus holds

df _(i+2,j) :=d _(i+2,j) −e _(i,j)

df _(i+3,j) :=d _(i+3,j) −e _(i+1,j)

[0070] This is an example of the subject of dependent claim 3, in itssimplest form, i.e. the embodiment wherein the subtractor (10)subtracts, in operation, said differences e_(ij), . . . e_(i+g−1,j) orpart thereof from the original luminance values d_(i+g,j), d_(1+2g−1,j)of pixels located on the same column . . . and the nearest neighbouringlines i+g . . . i+2g−1, respectively.

[0071] Vertical feedback over more than one pair of lines Next-next-Pixel Nearest pixel Next-nearest pixel nearest pixel Same pair of 0 0 00 lines Nearest pair of 0.75 0 0 0 lines Next-nearest 0.25 0 0 0 pair oflines Next-next- 0 0 0 0 nearest pair of lines

[0072] Simple two-dimensional feedback over one pixel and over one pairof lines, see FIG. 4 Next-next- Pixel Nearest pixel Next-nearest pixelnearest pixel Same pair of 0 0.75 0 0 lines Nearest pair of 0.25 0 0 0lines Next-nearest 0 0 0 0 pair of lines Next-next- 0 0 0 0 nearest pairof lines

[0073] In this example it thus holds:

d _(i+2,j+1) :=d _(i+2,j+1)−0.75*e _(i+2,j)−0.25*e _(i+1,j+1)

d _(i+3,j+1) :=d+3,j+1 −0.75*e _(i+3,j)−0.25*e _(i+1,j+1)

[0074] 75% of the error is fed back to the next pixel in the horizontaldirection and 25% to the pixels in the next pair of lines.

[0075] Two-dimensional feedback over more than one pixel and more thanone pair of lines Next-next- Pixel Nearest pixel Next-nearest pixelnearest pixel Same pair of 0 0.45 0.15 0 lines Nearest pair of 0.20 0.150 0 lines Next-nearest 0.05 0 0 0 pair of lines Next-next- 0 0 0 0nearest pair of lines

[0076] In this example part of the error is diffused to a previous pixel(i.e. nearest to the pixel in question to the left-hand side) at thenearest pair of lines. This particular pixel is displayed after thepixel in question. In preferred embodiments the error is also diffusedto the ‘previous’ pixel (i.e. seen in the direction in which the linesare written) on the nearest pair of lines. Instead of the coefficients0.45, 0.10, 0.20, 0.05, in a practical application, also thecoefficients {fraction (5/16)}, ⅛, ¼, {fraction (1/16)} appeared toyield good results.

[0077] In general, it is advantageous if the feedback coefficients F_(h)and F_(v) (or temporal feedback coefficients) diminish as the distance(in space or in time) increases. In all of the above tables, the totalof all feedback coefficients for a particular error is 1 (one) which isa preferred embodiment. However, the total sum of the coefficient coulddeviate from 1 and could be smaller than 1, in which case only a part ofthe error is diffused.

[0078] Temporal feedback may also be effected over more than one frame,for instance 75% diffused to the next frame and the remaining 25% to thenext-nearest frame.

[0079] A combination of temporal and spatial feedback may also beemployed. When use is made of a combination of temporal and spatialfeedback, the error may be and is preferably diffused not only to pixelsimmediately to the right of and below the pixel in question, but also toone or both of the pixels to the left of and above the pixel inquestion.

[0080] In embodiments, the feedback coefficients may be dependent on themagnitude of the error, wherein relatively small errors are diffused tonearest pixels and/or nearests pair of lines, (or not at all) whereasrelatively large errors are diffused over a larger area. Preferably, theerror diffusion coefficients are Y*(½″), for instance, ¾ and ¼, ormultiples of ⅛ or {fraction (1/16)} etc, the total sum of coefficientsbeing preferably 1. A threshold for the diffusion coefficients may bechosen, below which threshold errors are no longer diffused.

[0081] While the invention has been described in connection withpreferred embodiments, it will be understood that modifications thereofwithin the principles outlined above will be evident to those skilled inthe art, and thus the invention is not limited to the preferredembodiments but is intended to encompass such modifications. Morespecifically, the preferred embodiments relate to line doubling, but theinventions is also applicable when more than two lines are groupedtogether. The preferred embodiments also relate to diffusion of theerror to the nearest group of pixels, either to the right, or below,and/or to the same pixels in the subsequent frame. A diffusion of theerror to further next-nearest pixels or beyond and/or to a subsequentframe may be performed within the framework of the invention. It ispossible to interchange lines and columns. The invention is applicableto display devices where the subfield mode is applied. The invention canbe implemented by means of hardware comprising several distinctelements, and by means of a suitable programmed computer.

[0082] In the claims, any reference signs placed between parenthesesshall not be construed as limiting the claim. The word “comprising” doesnot exclude the presence of elements or steps other than those listed ina claim. The word “a” or “an” preceding an element does not exclude thepresence of a plurality of such elements. In the device claimenumerating several means, several of these means can be embodied by oneand the same item of hardware.

[0083] The mere fact that certain measures are recited in mutuallydifferent dependent claims does not indicate that a combination of thesemeasures cannot be used to advantage.

1. A matrix display device (1) comprising a display panel (5) having aset of lines (r₁ . . . r_(i) . . . r_(M)) of pixels, a data-processingunit (3) for receiving an input signal (D) representing successiveframes comprising original line luminance values of pixels (D, d_(i1) .. . d_(ij) . . . d_(iM)), to determine new luminance values of thepixels (C; c_(i1) . . . c_(ij) . . . c_(im)) on the basis of theoriginal line luminance values, the data-processing unit comprising aline-grouping means (LD), and a driver circuit (4) for supplying the newline luminance value data to said lines, said driver circuit (4) havingmeans for addressing groups i . . . i+g−1 of g lines with the samevalues, characterized in that the data-processing unit (3) furthercomprises a subtractor (10) for subtracting a correction value signal(E′) supplied by a processor unit (11) from the original line luminancevalues (D;d₁₁, d_(ij) . . . d_(mN)) to supply difference values (DF;df₁₁, . . . df_(ij) . . . df_(MN)) to the line-grouping circuit (LD), anerror determining circuit (12) for receiving the difference values (DF;df₁₁, . . . df_(ij) . . . df_(MN)) and said new luminance values ofpixels (C; c_(il) . . . c_(iM)) to supply an error signal (E) comprisinga set (e_(ij), . . . e_(i+g−1)) of the differences between the newluminance values (C; c_(ij), . . . c_(i+g−1,j)) of pixel j of groupingadjacent lines i, . . . i+g−1 and the difference values d_(ij), . . .d_(i+g−1,j) of pixel j of the same lines, and the processor unit (11),for receiving the error signal (E) to convert the error signal (E) intothe correction value signal (E′).
 2. A matrix display device (1) asclaimed in claim 1, characterized in that, in operation, the subtractor(10) subtracts said differences e_(ij), . . . e_(i+g−1,j) or partthereof from the original luminance values d_(i,j+1), . . .d_(i+g−1,j+1) of pixels located on the next column j+1 and the samelines i, . . . i+g−1, respectively.
 3. A matrix display device (1) asclaimed in claim 1, characterized in that, in operation, the subtractor(10) subtracts said differences e_(ij), . . . e_(i+g−1,j) or partthereof from the original luminance values d_(i+g,j), d_(i+2g−1,j) ofpixels located on the same column and/or neighbouring columns j−2, j−1,j+1, j+2 . . . and the neighbouring line and/or neighbouring lines i+g .. . i+2g−1, respectively.
 4. A matrix display device (1) as claimed inclaim 1, wherein frames are displayed subsequently, characterized inthat, in operation, subtractor (10) subtracts said differences e_(ij), .. . e_(i+g−1,j) or part thereof from the original luminance valuesd_(i,j), d_(i+g−1,j) of pixels located on the same column j and the samelines i . . . i+g−1 of the subsequent frame, respectively.
 5. A matrixdisplay device (1) as claimed in claim 1, wherein said luminance valuesare coded in subfields, said subfields consisting of a set of mostsignificant subfields and a set of least significant subfields, said newluminance values having, for all or part of the least significantsubfields, the same value for a group i, . . . i+g−1 of adjacent lines,and being addressed simultaneously to said group of lines.
 6. A matrixdisplay device (1) as claimed in claim 1, wherein said groups i . . .i+g−1 are pairs.
 7. A method of determining new luminance values of thepixels (C; c_(i1) . . . c_(ij) . . . c_(im)) on the basis of originalline luminance values (D, d_(i1) . . . d_(ij) . . . d_(iM)) to bedisplayed on a matrix display device (1) comprising a display panel (5)having a set of lines (r₁ . . . r_(i) . . . r_(M)) of pixels, the methodcomprising the step of data-processing to supply the new line luminancevalue data to said lines, and to address groups i . . . i+g−1 of g lineswith the same values, characterized in that the method comprises:subtracting (10) a correction value signal (E′) from the original lineluminance values (D;d₁₁, . . . d_(ij) . . . d_(mN)) to supply differencevalues (DF; df₁₁, . . . df_(ij) . . . df_(mN)), error-determining tosupply (12) an error signal (E) comprising a set (e_(ij), . . .e_(i+g−1,j)) of the differences between the new luminance values (C;c_(ij), . . . c_(i+g−1,j)) of pixel j of grouping adjacent lines i, . .. i+g−1 and the difference values d_(ij), . . . d_(i+g−1,j) of pixel jof the same lines, and processing (11) to convert the error signal (E)into the correction value signal (E′).
 8. A method as claimed in claim7, wherein said differences e_(ij), e_(i+g−1,j) or part thereof aresubtracted from the original luminance values d_(i,j+1), . . .d_(i+g−1,j+1) of pixels located on the next column j+1 and the samelines i, . . . i+g−1, respectively.
 9. A method as claimed in claim 7,wherein said differences e_(ij), . . . e_(i+g−1,j) or part thereof aresubtracted from the original luminance values d_(i+g,j), d_(i+2g−1,j) ofpixels located on the same column j and lines i+g . . . i+2g−1,respectively.
 10. A method as claimed in claim 7, wherein saiddifferences e_(ij), . . . e_(i+g−1,j) or part thereof are subtractedfrom the original luminance values d_(ij), d_(i+g−1,j) of pixels locatedon the same column j and the same lines i . . . i+g−1, of the subsequentframe, respectively.
 11. A method as claimed in claim 7, wherein saidluminance values are coded in subfields, said subfields consisting of aset of most significant subfields and a set of least significantsubfields, said new luminance values having, for all or part of theleast significant subfields, the same value for a group i, . . . i+g−1of adjacent lines
 12. A method as claimed in claim 7, wherein saidgroups i . . . i+g−1 are pairs.